1. Technical Field
The present invention relates to an image recording device which has a recording head which can, on the basis of input image data, simultaneously illuminate respective light beams from light sources of plural channels, and which records an image by scanning the light beams onto a recording material.
2. Description of the Related Art
Techniques (printing plate exposing devices), which use a sheet-shaped recording material (and in particular, a printing plate in which a photosensitive layer is provided on a support) and record an image directly by a laser beam or the like onto the photosensitive surface (emulsion surface) of the printing plate, have come to be developed. With such techniques, it is possible to rapidly record an image onto a printing plate.
In an automatic printing plate exposing device using the technique of recording an image onto a printing plate, in a state in which the printing plate is wound on the peripheral surface of a rotating drum, input image data is expanded into line image data (at an image expanding section). While the rotating drum is rotated at high speed (main scanning), on the basis of the line image data transferred in from the image expanding section, the output of the laser beam from a laser forming a portion of an exposure optical system is controlled so that a recording head (exposure head), which together with the laser forms the exposure optical system, moves along the axial direction of the rotating drum (subscanning). An image is thereby recorded on the printing plate.
Here, at the recording head, by outputting a plurality of laser beams simultaneously and scanning main scan lines of plural channels simultaneously, image recording can be made to be faster.
Japanese Patent Application Laid-Open (JP-A) No. 9-23320 (Japanese Patent No. 3179680) proposes an image recording device which can ensure a high speed of image recording while appropriately correcting tilting of the exposed image with respect to the original image so as to prevent distortion of the image. In particular, refer to paragraphs 0023 (FIG. 1) and 0028 (FIG. 3) of said patent.
Here, in an exposure optical system which carries out main scanning by plural channels simultaneously, there are cases in which the positions, in the main scanning direction, of the respective channels are offset from the recorded positions in the original image. A quantitative offset in pixels arises when, for example, a plurality of channels are offset alternately in the main scanning direction and are arranged in two or more rows.
Moreover, pixel offset in the main scanning direction also arises depending on the specifications for image recording, such as the setting of the resolution, the setting of the number of channels, the setting of interlacing/non-interlacing, and the like.
In order to correct this, it has been thought to hold a buffer (an FIFO, a memory or the like) for each channel, temporarily accumulate image data therein, and carry out positional correction by adjusting the reading timing for outputting in the main scanning direction.
Or, it has been thought to hold a buffer for each channel, and carry out positional correction by a combination of shifting the addresses read from a line memory at the time of temporarily accumulating the image, and shifting the image at the time of writing to the buffers.
However, in positional correction such as described above, in an exposure optical system in which the order of the channels changes, control for handling the respective orders is complex, and it is not easy to address such a situation.
As one example of a change in the channel order, in the case of setting the resolution, when the pitch of the channels which are simultaneously scanned is made to be a pitch which is more narrow than usual, such a change is handled by physically tilting the recording head with respect to the scan surface. In this case, if each channel is one line, the order of the channels does not change. However, if each channel is two or more lines, the channel order changes.
Further, there are cases in which the order of plural channels changes in accordance with the specifications for image recording, such as the setting of the resolution, the setting of the number of channels, the setting of interlacing/non-interlacing, and the like.
In particular, in the case of setting the resolution, when the pitch of the channels to be simultaneously scanned is to be made more narrow than usual, this is handled by physically tilting the recording head with respect to the scan surface. In this case, if each channel is one line, the order of the channels does not change. However, if each channel is two or more lines, the channel order changes.
When a change in the order of the channels is predicted, it is necessary to provide hardware corresponding to the respective channel orders. This leads to the structure of the device becoming complex and the number of parts increasing.